Mixture of cyclized rubber and resorcinol-formaldehyde resol



Patented Aug. 12, 1947 UNITED STATES PATENT OFFICE MIXTURE OF CYCLIZED RUBBER AND BE- SORCINOL-FORMALDEHYDE RESOL No Drawing. Application September 9, 1943. Serial No. 501,857

4 Claims.

This invention relates to heat-convertible compositions and particularly to compositions comprising heat-convertible aldehyde resols.

In the construction of many articles. the ultimate in strength and resistance to deformation can be secured only through lamination of various elements, by means of an adhesive, thus forming composite structures. This goal of ultimate strength has not heretofore been achieved in many instances because of the unavailability of suitable adhesives. Typical examples are structures composed of natural or synthetic rubber laminated to regenerated cellulose, steel. aluminum, etc.

It has now been found that, by blending cyclized rubber with thermosetting formaldehydemononuclear polyhydric phenol resols. there results a composition which can be used very advantageously as an adhesive in the manufacture of composite articles which are to be used at normal and at elevated temperatures.

The aforementioned cyclized rubber is a resinlike material, obtained by the action of acid reagents on rubber at elevated temperatures. Variations in the type of acid reagent and in the time and temperature of reaction results in a family oi resins. offeredin commerce under the trade names of Plioiite, Plioform," Thermoprene," etc.

It is an object of this invention to provide new class of compositions. It is another object to provide compositions which are flexible and heat-convertible. A further object is to provide compositions which have outstanding adhesive properties at normal and at elevated temperatures. A still further object is to provide adhesive compositions which are heat-convertible and which have outstanding power for bonding natural and synthetic rubbers to other surfaces. A general advance in the art and other objects, which will appear hereinafter, are also contemplated.

The above and other objects are accomplished by blending a cyclized rubber with a heat-convertible formaldehyde-mononuclear polyhydric phenol resol.

For practical reasons, the compositions of this invention are generally made by blending solutions in organic solvents of the cyclized rubber and thermosetting formaldehyde-mononuclear polyhydric phenol resols. In place of using solutions in organic solvents, the cyclized rubber and thermosetting aldehyde resol can be dispersed or emulsified in a water containing medium and the dispersions then blended. If desired, however, the cyclized rubber and thermosetting aldehyde resol can be mixed in the dry state to produce a homogeneous blend.

The examples, which follow, illustrate the principles and diverse embodiments of the invention. including those contemplated for carrying out the same. In the examples, parts are by weight unless otherwise stated.

EXAMPLEI A cyclized rubber is prepared by masticating 1000 parts of smoked sheet rubber on a mill at C. until it forms a smooth, continuous sheet, To the rubber on the mill is added 500 parts of a carbon black, sold under the trade name of Micronex," and the mixture worked on the mill until the carbon black is homogeneously dispersed in the rubber. The blend is removed from the null, cut into smal1 pieces and dissolved in 4500 parts of xylene. To the solution is added 22.5 parts of concentrated sulfuric acid and 200 parts of phenol and the mixture heated with stirring for 16 hours at 115 C. At the end of this period the acid is neutralized by adding, with stin'ing, 30 parts of ethanolamine. The mixture is then cooled to 25 C.

A resorcinol-formaldehyde resol is prepared by dissolving 24 parts of paraformaldehyde in 162 parts of normal butanol containing 0.24 part of potassium hydroxide and then adding to this solution with stirring at 20 0., 30 parts of resorcinol, followed by 1 part of of a 25% solution of phosphoric acid in ethanol.

Two hundreds parts of the cyclized rubber, prepared as described above, is mixed with stirring with 88 parts of the resorcinol-formaldehyde resol solution prepared as described above. To the blend is added with stirring 16 parts of a 10% solution of hexamethylene-tetramine in chloroform and the resulting composition used as an adhesive in laminating rayon, nylon, and cotton to natural and synthetic rubbers as follows Weighed strips of square woven rayon, nylon and cotton fabrics are coated with the above adhesives, the coated strips are heated for from 5 to 30 minutes at 70 to C., cooled, and then weighed to determine the amount of adhesive deposited on the cloth. The coated strips are then pressed onto carcass stocks of natural rubber, GRS 1 (Buna S and neoprene calendered onto a cotton fabric backing for reenforcement and compounded for vulcanization. The assemblage of carcass and cyclized rubber/thermosetting aldehyde resol coated fabric is placed in a mold and heated at 140 C. to 145' C. until the bond strensth of 25 lbs. per linear inch at 25 C. rubber is vulcanized and the adhesive has heat but is completely ineiiective at 100 C., the bond converted. Thereafter, the composite is removed strength having fallen to 12 lbs. per linear inch. 1mm the mold. cooled and bond strength deter- At such temperatures, and even up to 140 C'. or mined by measuring the pull in pounds per lin- 5 higher, combinations containing the thermosetear inch required to separate the rubber irom ting iormaldehyde-mononuclear polyhydric phethe adhesive coated fabric. The results are sumnol resol retain substantially all 01 their original marized in Table I below. bonding eflectlveness.

Tsar: I

Lamination of natural and synthetic rubbers to rayon, cotton and nylon Bond strength, Adhesive lblJin. at- Febrie Adhesive Composition Rubber Stock Loading,

Per Cent 2. i. 6 None an 1,1 0 Head rubber oi as 1 1% g H: yc Resoreinol-iormaldebyde resol 4:, 5 a: 9

Adhesive oi Er. l as so ;.0 5 mm an 210 Nylon u a Adhesive 01 Ex. 1 a 82 1; 0 tton 0 Adhesive cl Ex. 1 2% a 1 A 75/25 butadiene/styreue interpolymer prepared by procedures analogous to those of U. 5. Patent 1 938 731. I A 2-ohloro-l,3-butadiene (chloroprene) polymer, prepared according to U. 8. Patent 2,204,173,

EKAMIP'IEII EXABEPLEIII A cyclized rubber is prepared by masticating 35 A series of cyclized rubbers is prepared as 01- 100 parts of smoked sheet rubber on a mill at 70 lows from neoprene and GRB C. until it forms a smooth, continuous sheet. The A. Fifty parts oi GRS 1 is dissolved in 450 parts rubber is removed from the mill, cut into small 01 xylene and to this solution is added parts of pieces and dissolved in 900 parts of xylene. To meta-cresol and 2.3 parts of concentrated sulthis rubber solution is added a mixture of 2.25 40 iuric acid and the mixture is heated with stirring parts of concentrated sulfuric acid and parts ior 48 hours at 120 C. of phenol and the mixture heated for 13 hours at B. One hundred parts of milled neoprene is 100 to 115 C. with stirring, after which there dissolved in 100 parts of xylene and to this soluis added 3 parts 01 ethanolamine, and the mixtion is added 2.25 parts of concentrated sulfuric ture cooledto C, acid, 1 part 0! boric acid, and 15 parts of meta- An adhesive composition, prepared by blendcresol and the mixture is heated with stirring for ing the above cyclized rubber with the resorcinol- 10 hours at 110 to 120 C.

formaldehyde resol, described in Example I, was A series oi adhesive compositions, comprising evaluated in the bonding of natural rubber to blends of the cycllzed rubbers prepared as derayon. The composition of the blend and the scribed above with the aldehyde resols listed bebond strengths obtained, in comparison with low, is prepared and evaluated in the bonding of cyclized rubber alone and with the resol alone, natural rubber, GRS, and neoprene to nylon and are listed in Table II. rayon. The results are shown in Table III.

Tsar: II

Lamination of natural rubber to rayon Bond Strength Loading lbsJin. at- Bubber Compound Parts Thermosetting Resol Parts Catalyst Parts :31 Fabc r None-.-- 10 2.0 1.5 Resorclnolji'ormaldehyde-- l0 NaOlEL. 0.05 12 6 t2 s- .0

Besorcinolliormaldehyde" 10 Hem 1.0 10 30 31 I Henmethylenetetramino.

From the data in Tables I and II, it is appar- (i) To 30 parts of the solution in xylene of ent that the adhesives, containing cyclized rubcyclized rubber (A) is added 3 parts of a 50% sober and a thermosetting iormaldehyde-mononulution of a resorcinol-iormadlehyde resol in norclear polyhydric phenol resol, are unexpectedly mal butanol, prepared as described in Example better in bond strength than either cyclized rub- I, and 1.5 parts of a 10% solution of hexamethylher alone or the thermosetting aldehyde resols enetetramineinchloroform. alone. This is particularly true at elevated tem- (2) To 30 parts or the solution in xylene of peratures for the cyciized rubber, which yields a cyclized rubber (A) is added 6 parts of a 25% so- 5 lution of a resorcinol-iormaldehyde resol, prepared by dissolving 40 parts of pararormaldehyde in 270 parts or normal-butanol containing 0.4 part of potassium hydroxide, adding 50 parts of pending upon the use to which the composition is to be put. Generally. the preferred compositions for use as adhesives contain from 25 to 90% or the cyclized rubber by weight, based on total resorcinol, and allowing the mixture to stand at g solids. and the thermosetting rose! is the reaction 25 C. for 24 hours, and 3 parts of a 10% solution product of formaldehyde with a mononuclear of hexamethylenetetramine. po yhidric phenol. especially the reaction prod- 8. To 24 parts oi. a 10% solution in xylene 01' not of formaldehyde with either resorcinol. pyrocyclized rubber (B) is added 0.1 part or maggallol, or phloroglucinol. Percentages outside nesium oxide, 5 parts or a 25% solution or a re- 10 this range, as iron 5 to 95%, can be used, howsorcinol-iormaldehyde resol in normal butanol, ever, especially in applications where exceptionprepared as in Example I, and 1.25 parts or a 10% ally high bond strengths are not critical. solution or hexamethylenetetramine in chloro- In the lamination oi nylon and rayon to natural i'orm. and synthetic rubbers, best results are obtained Tm: m

Rubber-fabric lamination bonded with thermo-settma resol/cyclized rubber compositions Adhesive Composition R hm 011 im 59$ u a or Stock oent li y Cycllned Rubber Parts Thermosettlng Besol Parts Catalyst Parts 25 0 100 0.

l 6. 5 1.0 None iii 9.0 1.0 Rayon. Cyclized on-s {3 53 ,3 an Besoroinol/iormaldehydal0 Hera l. 0 gill 5(7) 7. 0 1. 5 N d o. s 1.3

i0 27 is 2) Resorcinol/iormaldehydm- 10 Hana 2. 0 m 72 2s 10 8. 0 2. 0 None Rayon. Cyalized Neoprene" g; ,2 20 Resorcinolliormaldehyden l0 Hers 1.0 30 33 m 1 A 75/25 butsdienelstyrene interpolymer, prepared by procedures analogous to those of U. 8. Patent 1,988,731.

' Hexamsthylonetetramine.

ExAMPLEIv Following the procedure described in U. 8. Patent 1,668,236, there is added to 100 parts of rubber on a mill 2.5 parts of concentrated sulfuric acid mixed with 2.5 parts of a carbon black, sold under the trade name of Micronex" and the mixture worked on the mill until the carbon black is homogeneously dispersed in the rubber. The blend is removed from the mill and heated in an oven for 20 hours at 130 C. The resulting product is somewhat tacky and resembles very lightly vulcanized rubber. The cyclized rubber thus obtained is cut into small pieces and dissolved in xylene to form a solution containing solids by weight.

A resorcinol-formaldehyde resol is prepared by dissolving 24 parts of parai'ormaldehyde in 162 parts of n-butanol at about 90 C., cooling, and

then adding to this solution with stirring at C. parts of resorcinol.

Forty-two parts of the oyclized rubber solution, prepared as described above, is mixed with stirring with 13.5 parts of the resorcinol-formaldehyde resol solution prepared as described above. To this mixture is added, with stirring, 7 parts 01' a 10% solution of hexamethylene-tetramine in chloroform, and the resulting blend used as an adhesive in laminating nylon to natural rubber according to the procedure described in Example I. The nylon fabric containing approximately 14% adhesive is found to exhibit an adhesion at 25 C. of 29 lbs./in. to the rubber carcass stock.

In the preparation oi the compositions of this invention, the ratio of cyciized rubber to thermosetting iormaldehyde-mononuclear po y ydric phenol resol can be varied over a wide range, de-

with blends of cyclized rubber and formaldehydemononuclear polyhydric phenol resols varying in composition from about 60/40 to /20 and these compositions, therefore. constitute a preferred embodiment oi this invention.

Cyclized rubbers may be prepared in any one of several ways, and their composition and properties may vary somewhat, but. however prepared, they are thermoplastic and have less chemical unsaturation than natural rubber. They appear to have an empirical formula of (CsHs) and to be condensation derivatives of rubber. The term condensation is used in the same sense that it is employed by Cohen (page 245) of his "Organic Chemistry for Advanced Students," 1909 edition) namely:

"Condensation may, then, be defined as the union of two or more organic molecules or parts of the same molecule with or without the elimination of component elements, in which the new combination is efiected between carbon atoms."

In the condensation, various reagents may be employed for converting rubber into the cyclizecl rubber. In one mode of preparation, a solution (the reaction with the rubber is advantageously carried out in solution) of the rubber in benzene or xylene is boiled for an hour or two and then, while continuing the boiling under a reflux condenser, up to 10% (based on the amount of rubher) of a conversion agent such as stannic chloride, is added. The heatin is then continued for perhaps several hours, or until the desired reaction has taken place. The condensation derivative of the rubber is isolated by pouring the reaction mass into water, acetone, alcohol (methyl, ethyl, etc.) and the like.

'I'in tetrachloride apparently reacts with the rubber to form a tin chloride addition product of rubber (or cyclized rubber) which probably has the formula (CsHshSnCh. The tin and chlorine split on upon drowning the reaction product, leaving the cyclized rubber hydrocarbon. In this procedure aluminum chloride, ferric chloride, chromic chloride or another halide of an amphoteric metal, may replace the tin chloride.

The deformation point (point at which plastic flow is detectable) in any one case depends upon the type of rubber treated, the amount and type of catalyst, and the time and temperature used in the conversion. By varying these factors products varying in deformation point from 30 to 105 C. can be obtained. Products in the lower deformation range are ordinarily used in the practice of this invention.

The cyclized rubber called Pliolite," is a thermoplastic rubber derivative made by condensing rubber with a catalyst of the tin chloride type. Specific details of its preparation, structure, etc., are set forth in Rubber Age for April, 1939.

The cyclized rubbers, made by treating a natural rubber or a synthetic rubber in solution with sulfuric acid and a phenol as described in the examples, constitute the preferred products for use in the practice of this invention. Other useful products are made by the procedure described in U. 5. Patents 1,605,180; 1,668,235; 1,668,236; 1,668,237; 1,745,926; 1,782,140; 1,747,188; 1,846,- 247; 1,852,294; 1,852,295; 1,852,345; 1,852,346; 1,853,334; 2,050,209 and 2,052,931. Of these products, the preferred cyclized rubbers are those which are resilient and elastic like soi't vulcanized rubber. These products are in general obtained by reacting two or three parts of concentrated sulfuric acid or two to five parts of a phenol sulfonic acid with the rubber.

The examples have illustrated the use of natural rubber and such synthetic rubbers as GRS and neoprene in the preparation of cyclized rubbers. In place of these materials, such naturally occurring products as gutta-percha and balatta as well as such rubber-like materials as the polymers oi butadienes with other polymerizable organic compounds containing olefinic unsaturation can be used, exemplified by the polymer obtained by polymerizing 2-chlorobutadiene-1,3 with 2-methyl butadiene-l,3, or butadiene-l,3 with acrylonitrile, etc.

In place of formaldehyde there can be used other aldehydes, and materials which under the conditions of reaction liberate formaldehyde, in the preparation of the thermosetting aldehyde resols. Examples of such materials are paraformaldehyde, hexamethylenetetramine, 1,3,5-trioxane, acetaldehyde, buty'raldehyde, chloral, furfural, benzaldehyde and the like.

The thermosetting resols can be made from various mononuclear polyhydric phenols such as hydroquinone, catechol, pyrogallol, phloroglucinol, orcinol, and the like. The polyhydric phenols and particularly the dihydric mononuclear phenols are preferred because thermosetting aldehyde resols made therewith yield, with cyclized rubber, adhesives showing particularly good bond strengths at elevated temperatures.

To th compositions of this invention can be added, if desired, any of the usual ingredients usually used in compounding rubber, e. g., pigments, fillers, vulcanizing ingredients and antioxidants.

The compositions of this invention find particular utility in the lamination of rayon, cotton,

and nylon to natural and synthetic rubbers in the lubrication of reenforced belting, tire carcasses and the like. In place of the enumerated textile materials. there can be used textiles based on organic cellulose derivatives, e. g., cellulose acetate, etc, polymers of vinyl and vinylidene compounds, silk. wool, casein and the like. In instances where the textile material will not withstand the temperature necessary for vulcanlzation of the rubber, a rubber stock is used which is susceptible of being vulcanized at the ordinary or moderately elevated temperatures, and the thermosetting formaldehyde-mononuclear polyhydric phenol resol is catalyzed so that it will convert under the same conditions as those used in vulcanizlng the rubber. A particularly usei'ul application is in the manufacture of composite articles made by laminating natural or synthetic rubber to a material in the form of a film, c. 8., nylon and cellulose derivatives, etc.

The utility of the compositions oi this invention as adhesives is not restricted to laminatlons involving the bonding of textile to natural and synthetic rubbers but they can also be used to advantage in laminating metals, e. g., steel, tin, aluminum, and the like to natural and synthetic rubber, to wood, textiles, etc., wood to wood, wood to metals, metal to metal, metal to textile, etc.

Some of the compositions embraced within the scope of this invention, particularly those containing from 40 to 90%, based on total solids, of the thermosetting formaldehyde-mononuclear polyhydrlo phenol resol are useful as molding and coating compositions.

I claim:

1. A composition for bonding textile materials to rubbery polymers comprising a blend of a cyclized rubber, obtained by heating a solution of a member of the group consisting of natural rubber, rubbery polymers of 2-chlorobutadiene- 1,3 and rubbery polymers of butadiene-1,3 with a small proportion of sulfuric acid and a small proportion of a phenol, and a heat-convertible resol which is the reaction product of formaldehyde and resorcinol only, the cyclized rubber constituting from 25% to by weight of the total solids of the composition.

2. A composition for bonding textile materials to rubbery polymers comprising a blend of a cyclized rubber, obtained by heating a solution of natural rubber with a small proportion of sulfuric acid and a small proportion of a phenol, and a heat-convertible resol which is the reaction product of formaldehyde and resorcinol only, the cyclized rubber constituting from 25% to 90% by weight of the total solids oi the composition.

3. A composition for bonding textile materials to rubbery polymers comprising a blend of a cyclized rubber, obtained by heating a solution of a rubbery polymer of 2-chlorobutadiene-1,3 with a small proportion of sulfuric acid and a small proportion of a phenol, and a heat-convertible resol which is the reaction product of formaldehyde and resorcinol only, the cyclized rubber constituting from 25% to 90% by weight of the total solids of the composition.

4. A composition for bonding textile materials to rubbery polymers comprising a blend of a cyclized rubber, obtained by heating a solution of a rubbery polymer of butadlene-L3 with a small proportion of sulfuric acid and a small proportion of a phenol, and a heat-convertible resol which is the reaction product of formaldehyde and resorcinol only, the cyclized rubber constitutena e fine from 25% to 90% by weight of the total solids Number Name Date of the composition. 2,300,367 Harmon Oct. 2'7, 1942 HERMAN E. SCI-IROEDER. 2,301,359 Lannlng NOV. 17, 1942 2,328,534 Carson Au 31, 1943 RE RE G S CITED 5 1,970,835 Banner Aug. 21, 1934 The following references are of record in the Harkms M813 71 1944 me of this patent: 2,300,368 Harmon Oct. 27, 1942 2,072,508 Mahlman et al. Mar. 2, 1937 UNITED STATES PATENTS OTHER REFERENCES Number Name Date 19 2,128,229 Church Aug. 30, 1938 Chem. and Eng. News," Biggs et at, June *5, 2,291,208 Brown et a1. July 28, 1942 1943, pages 962, 963.

Gertificate of Correction Patent No. 2,425,348. August 12, 1947. HERMAN E. SCHROEDER It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Column 4, Table II, in the heading to the seventh column thereof, for Loading on Fabric, per read Loading on Fabric, per cent by Weight and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 30th day of September, A. D. 1947.

THOMAS F. MURPHY,

Assistant Uammisaioner of Patents.

ena e fine from 25% to 90% by weight of the total solids Number Name Date of the composition. 2,300,367 Harmon Oct. 2'7, 1942 HERMAN E. SCI-IROEDER. 2,301,359 Lannlng NOV. 17, 1942 2,328,534 Carson Au 31, 1943 RE RE G S CITED 5 1,970,835 Banner Aug. 21, 1934 The following references are of record in the Harkms M813 71 1944 me of this patent: 2,300,368 Harmon Oct. 27, 1942 2,072,508 Mahlman et al. Mar. 2, 1937 UNITED STATES PATENTS OTHER REFERENCES Number Name Date 19 2,128,229 Church Aug. 30, 1938 Chem. and Eng. News," Biggs et at, June *5, 2,291,208 Brown et a1. July 28, 1942 1943, pages 962, 963.

Gertificate of Correction Patent No. 2,425,348. August 12, 1947. HERMAN E. SCHROEDER It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Column 4, Table II, in the heading to the seventh column thereof, for Loading on Fabric, per read Loading on Fabric, per cent by Weight and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 30th day of September, A. D. 1947.

THOMAS F. MURPHY,

Assistant Uammisaioner of Patents. 

